A student was analyzing an unknown containing only Group IV cations. When the unknown was treated with 3M (NH4)2CO3 solution a white precipitate formed. Because the acetic acid bottle was empty , the student used 6M HCl to dissolve the precipitate. Following the procedure of this experiment the student then added 0.10M K2CrO4 solution as directed, and no percipatation formed. Oxalic acid was added to the solution and no precipitation formed.
a. what mistake sis the student make?
b. How did the mistake affect affect the tests for the cation in solution